1. Field of the Invention
This invention relates to refrigeration apparatus and in particular to means for defrosting such apparatus.
2. Description of the Prior Art
In one improved form of ice maker-type of refrigeration apparatus illustrated in my U.S. Pat. No. 3,230,736, owned by the assignee hereof, a slab of ice is formed on an evaporator structure over which water is circulated to build up the desired slab. Upon completion of the formation of the slab, which may be determined by suitable sensors or other suitable means, the flow of water is terminated and the evaporator is heated to free the formed slab therefrom, permitting it to pass onto a grid means for cutting the slab into desired smaller cubes.
The evaporator may be heated during the slab removal defrosting operation by suitable means.
One conventional method of defrosting an evaporator comprises operating the refrigeration system reversely so as to provide hot refrigerant gas to the evaporator rather than to the condenser to which the hot refrigerant is delivered in the normal refrigeration operation of the system. The present invention is concerned with an improved means for effecting such hot gas defrosting, or heating, of an evaporator in such a refrigeration system.
Another form of such slab ice maker apparatus is shown in U.S. Pat. No. 2,747,375 of Joseph R. Pichler. In said patent, a bypass line is provided for conducting refrigerant fluid from a receiver through a solenoid valve to the evaporator. The receiver is connected to the condenser. The refrigeration apparatus comprises an expansion valve apparatus wherein an expansion valve is provided in the conduit leading from the receiver with a thermostatic control thereon with the expansion valve controlling the flow of refrigerant to the evaporator during normal operation of the system. A second valve is provided in a second conduit leading to the evaporator for bypassing the expansion valve during a defrosting operation. The refrigeration fluid is provided to the evaporator from the receiver during both the refrigeration and defrosting cycles.
In the U.S. Pat. No. 3,338,065, of Carlyle M. Ashley, an accumulator is provided for storing refrigerant fluid to be provided to the condenser during a defrosting operation. Refrigerant flow from the accumulator is limited by a restrictor to permit the condenser to completely vaporize the liquid delivered from the accumulator before delivery thereof to the evaporator.